DRAFT ACT WATER RESOURCES ENVIRONMENTAL FLOW GUIDELINES (Based on disallowable Instrument DI2013-44 ACT Environmental Flow Guidelines & recommendations in supporting report reviewing 2013 Environmental Flow Guidelines (Dusting et al. 2017)) © Australian Capital Territory, Canberra 2018 Photos taken by David Jenkins, Mark Jekabsons, Danswell Starrs and Antia Brademann This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without written permission from: Director-General, Environment, Planning and Sustainable Development Directorate, ACT Government, GPO Box 158, Canberra ACT 2601. Telephone: 02 6207 1923 Website: www.environment.act.gov.au Privacy Before making a submission to this discussion paper, please review the Environment, Planning and Sustainable Development Directorate’s privacy policy and annex at www.environment.act.gov.au/about/ privacy. 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For more information on these services visit www.relayservice.com.au CONTENTS EXECUTIVE SUMMARY 1 4 ECOLOGICAL OBJECTIVES FOR ACT AQUATIC ECOSYSTEMS 27 1 INTRODUCTION 5 5 ENVIRONMENTAL FLOWS FOR PARTICULAR 1.1 Background 5 ECOSYSTEMS 33 1.2 Purpose of the guidelines 6 5.1 Water supply ecosystems 38 1.3 National responsibilities 6 5.2 Natural ecosystems 42 1.4 Statutory basis for environmental flows 5.3 Modified ecosystems 43 in the ACT 8 5.4 Urban ecosystems 46 1.5Review of the guidelines 9 6 MONITORING AND ASSESSMENT 49 2 DETERMINATION OF ENVIRONMENTAL FLOWS 11 6.1 Applying the framework to the different 2.1 Basis for determination of environmental flows11 ecosystems and flow components 50 2.2 Adaptive management 11 2.3 Economic and social issues 12 GLOSSARY AND BIBLIOGRAPHY 53 2.4 Water quality issues 12 2.5 Impoundment release structures 12 APPENDICES 61 2.6 Augmentation of stream flows 13 Appendix 1: Scientific Basis For Recommendations 2.7 Climate change 13 From 2004 Review Of The Environmental 2.8 Groundwater 15 Flow Guidelines (1999) 61 2.9 Upstream influences 16 Appendix 2: Recommendations From 2010 2.10 Types of ecosystems 16 Review Of The Environmental Flow Guidelines (2006) 64 Appendix 3: 3 ENVIRONMENTAL FLOW APPROACH Scientific Basis For Recommendations ADOPTED 19 From 2017 Review Of The Environmental 3.1 Techniques for calculation of flows 20 Flow Guidelines (2013) 65 3.2 Components of environmental flows 21 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES C D DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES EXECUTIVE SUMMARY The Environmental Flow Guidelines are an instrument under the Water Resources Act 2007 that set out the flow requirements needed to maintain aquatic ecosystems. The Guidelines have been developed using the most up to date scientific information available, and will be used with Water Resource Management regulatory instruments under the Water Resources Act 2007, water available from areas determination and Water Management Areas determination to manage ACT water resources. Environmental flows, for the purposes of the Water Resources Act 2007, are specified in Table 3 of Section 5 for each ecosystem category and each specific reach. The Environmental Flow Guidelines apply to all rivers, streams, lakes and ponds in the ACT. The 2018 Environmental Flow Guidelines replace the 2013 Environmental Flow Guidelines. DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES 1 PURPOSE OF ENVIRONMENTAL FLOWS Environmental flows describe the quantity and timing The base flow is the flow component contributed of water required to sustain freshwater ecosystems. mostly by groundwater, and is the minimal volume of water that the stream needs to support the fish, We rely on our waterways for a range of functions plants, insects, and protect water quality. The volume including biodiversity and conservation, irrigation of the base flow is determined for each month for each and domestic water supply. Waterways need to be stretch of stream or river. healthy to provide these functions. The natural flows in ACT streams are highly variable. Rivers and streams The purpose of the small and larger floods, termed naturally have periods of both very low and very riffle, pool, and channel maintenance flows, is to move high flows. Flows in our streams also vary seasonally out sediment deposits and maintain channel form. with the higher flows usually occurring in the spring The movement of sediment is important for months. The Environmental Flow Guidelines identifies maintaining healthy aquatic ecosystems. Riffles are those components of flow from this variable flow the shallow fast flowing sections of the river. The regime necessary to maintain stream health. One way riffle maintenance flows scour out fine sediment that to do this is to specify environmental flows that mimic accumulates in riffles, damaging these habitats for the flows that would occur naturally. In more heavily fish, water plants and other aquatic life. The pool and used systems such as water supply catchments it may channel maintenance flows scour sediment from pools be necessary to protect specific components of the and ensure the river maintains its natural channel form. flow regime to keep aquatic ecosystems healthy. Special purpose flows are flows designed for a In highly modified ecosystems, the environmental particular ecological need, for example the flow flows needed to ensure critical processes occur and needed to encourage breeding of a species of fish, or provide habitat, may be very different to the natural to protect habitat of a frog species. The Guidelines flow regime that occurred before development. make provision for special purpose flows should they be identified. However no special purpose flows are currently specified in the Guidelines. COMPONENTS OF ENVIRONMENTAL FLOWS Impoundment drawdown levels are the levels that a reservoir, lake or pond needs to be kept within, so that To account for natural variability, the Environmental impacts on macrophytes, sediment processes and Flow Guidelines include protection of particular water quality do not result in adverse changes to the components of the natural flow. These are: state of the ecosystem. Static impoundment levels can > base flow; result in a limited fragile ecosystem dominated by a few species of flora and fauna even though the biomass > small floods (riffle maintenance flows); can be high. Excessive fluctuations in impoundment > larger floods (pool or channel maintenance flows); levels can result in a denuded barren water body that > special purpose flows; and supports little biomass and low biodiversity. > impoundment drawdown level. 2 DRAFT ACT ENVIRONMENTAL FLOW GUIDELINES > HOW ENVIRONMENTAL FLOWS Flows specified for these catchments are the minimal ARE PROVIDED requirement for healthy aquatic ecosystems, while ensuring that both water supply and conservation In the ACT environmental flows are provided in one of objectives can be met. This approach is appropriate two ways: either by releases or spills from dams, or by for these catchments as the intensive monitoring of the restricting the volume of water that can be abstracted system allows adaptive management to be implemented from a water management area. In the ACT the volume if adverse effects are detected. of water available for abstraction within each water Special rules for drought periods have also been specified management area is limited to the volume remaining for these catchments. The Guidelines recognise that after environmental flow volumes have been provided. during dry times when the urban population faces water Abstraction rules are also applied to ensure that licensed restrictions, it is appropriate that environmental flows abstractors do not impact on waterways during critical also be reduced. flow events such as very low flows, flooding flows or cause excessive drawdown levels. The ACT only abstracts up to about 10% of available flows on average, with the remaining 90% effectively environmental flows. In ENVIRONMENTAL FLOWS IN URBAN PURPOSE OF addition, only the water supply dams significantly modify CATCHMENTS ENVIRONMENTAL FLOWS flows in downstream river reaches. Urbanisation has caused considerable modification to the streams flowing through urban areas. The increase in Environmental flows describe the quantity and timing impervious surfaces, including roads, roofs and car parks, of water required to sustain freshwater ecosystems. ECOLOGICAL OBJECTIVES FOR